You have the ability to utilize CSS styling in order for the background image to adjust automatically based on the size of the table.
Here is the code snippet:
.tableBckImg
{
background:url(http://www.placehold.it/300x300);
background-repeat:no-repeat;
background-size:100% 100%;
}
<table cellspacing="0" cellpadding="0" border="0" class="tableBckImg">
<tr>
<td width="50" align="center">1</td>
<td width="50" align="center">2</td>
<td width="50" align="center">3</td>
</tr>
<tr>
<td width="50" align="center">4</td>
<td width="50" align="center">5</td>
<td width="50" align="center">6</td>
</tr>
</table>
You can modify the number of rows and columns to observe how the background image expands or shrinks accordingly, as demonstrated in this fiddle example.
In the provided example, the background image has dimensions of 300x300 pixels.